Aldl connection corrupted data when engine running

[AlexanderHL]

Managed to get the winaldl software up and running perfectly trough usb FT232 adapter.
It provides a steady stream of data on all things when car (89 g20) is in ignition on, engine off.
However with engine running the datastream gets corrupted somehow, and values recorded takes on all sort of numbers.

On the usb adapter i can change from 5 to3,3 volts, but this didn't change the results.
So Im thinking it could be one or more of several things?

Bad ground somewhere. wiring harness
Bad alternator, or alternator ground?
Ignition coil, ground
Spark plug wires running to close to the main wiring harness causing interference.

Anyone has experience with this, suggestions would be appreciated :)

BR
/Alex

[1project2many]

89 G20 will have slow updates. What is an example of the corruption you're seeing?

[steveo]

as a general rule on any car if the log data is clean when engine is off, but becomes corrupt with engine on,

- try running with alternator disconnected. if situation improves, replace alternator (failed alternator rectifier is introducing AC current into the system)
- try jumper cabling chassis to engine to ECM. if situation improves you have a shoddy ground cable
- try firing engine up in the dark and mist water all around the engine with a spray bottle. if you see sparks, you have a spark plug wire or coil or something with insulation breakdown producing RF that is screwing with your data stream

[AlexanderHL]

Thanx for the suggestions :)


The setup i have now is a separate distributor connected on the side driven by battery drill, so im able to produce the error on demand, with ignition on, engine off.
It only occurs when ignition coil gives spark. Single spark plug grounded to engine block.

I contacted the creator of winaldl who did his best to help me troubleshoot with an additional log function (big thanks to him :)). It showed that data corruption occurs only when ignition coil fires.

I have tested all main grounding points and ground in harness, all good, around 0,5 to 1 ohm.
I also tried to ground wiring harness where ecm ground joins together to block, however no improvement.

Alternator belt off
Injectors disconnected
Radio/hifi disconnected
Brand new ignition coil.
2 different ignition control modules

Same error, so im right now thinking if something on 1227747 ecu is broken. I do have a capacitor on the board that looks a bit sketchy, which could be a part of some sort of low pass filter. unsure




as a general rule on any car if the log data is clean when engine is off, but becomes corrupt with engine on,

- try running with alternator disconnected. if situation improves, replace alternator (failed alternator rectifier is introducing AC current into the system)
- try jumper cabling chassis to engine to ECM. if situation improves you have a shoddy ground cable
- try firing engine up in the dark and mist water all around the engine with a spray bottle. if you see sparks, you have a spark plug wire or coil or something with insulation breakdown producing RF that is screwing with your data stream

[updatelee]

You never mentioned an inverter/charger but by chance are you using one ? I was getting horrible corrupt data, more packets lost then received. Then I unplugged the laptop so it was running on battery power and data was perfect. Im guessing it was the switching power supply creating interference, who knows. Try running your laptop on battery power alone and see if there is any change